Atopic immediate sensitivity is the chief manifestation found in animals suffering from bronchial asthma, seasonal pollinosis, allergic rhinitis, urticaria, allergic conjunctivitis, food allergy and anaphylactoid reactions. The substances most frequently responsible for clinically manifest sensitivities are plant pollen, animal feathers and danders, dust, milk and wheat, whether inhaled or ingested.
Atopic hypersensitivity is found in man, dog and other animals. Its occurrence is exceptionally found in the lower animals.
The presence of antibodies associated with atopic reactions in the host serum is established by the passive sensitization of the skin of a normal recipient, after injection of serum from a sensitized host into a skin site followed by injection of antigen into the same area 24 hours later, resulting in a local hive. This is commonly referred to as the Prausnitz-Kustner (P-K) reaction.
The antibody associated with atopic hypersensitivity possesses distinctive features in that it does not in all forms precipitate with its antigen, fails to pass the placenta from mother to fetus, has special affinity for the skin, frequently lacks specificity toward an individual antigen in an individual sensitized by a variety of antigenic factors and is usually labile at about 56.degree.C after 2 hours.
The homocytotropic antibody found in or induced in the rat is related in function and reaction to immunoglobulin E (reagin or IgE) found in the human. The correlation between homocytotropic antibody in the rat and IgE in the human has been established through the common effects obtained from chemical reactions, immunological reactions and drug responses in the two species hosting those antibodies. In the human, reagin is the antibody responsible for atopic immediate hypersensitive reactions. In the rat, the homocytotropic antibody is responsible for atopic immediate hypersensitive reactions.
In theory, reagin, influences the cell membrane of a mast cell by reacting with an antigen, to initiate the reaction(s) within the mast cell which ultimately releases a mediator such as Bradykinin, SRS-A (slow reacting substance-A), histamine, and other unknown substances. The mediator effects a change in surrounding cell wall permeability permitting a rapid change in flow or exudance of mediator(s) from the cells, resulting in an allergic attack symptom. The various methods commonly employed to relieve the symptoms of allergic attack, none of which are considered to be quite acceptable, are to (1) avoid attack by the antigen, (2) block the production of antibody with an immunosuppressant, (3) block the action of the mediators on the cell under attack by administration of anti-histaminics, anti-5-hydroxy-tryptamine (5-HT) or anti-inflammatories, or (4) stimulate the cell under attack to negate the action of the mediator through the action of bronchodilators such as Isoprel or a Xanthine.
The only commercial compound known to date to operate as an anti-allergic primarily by blocking reaction(s) within the mast cells, thereby preventing the production and release of mediators, is disodium cromoglycate (INTAL).